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Optically-pumped semiconductor lasers

Optically pumped semiconductor lasers (VECSELs) uses a multilayer structure of semiconductor materials as the active gain medium. The chip includes quantum wells - giving rise to laser emission - and a reflective Bragg mirror. The active structure is pumped by a high power laser diode and placed in a cavity closed by a mirror. Very high output powers are obtained with such lasers. Furthermore, the versatility of semiconductor materials allows to operate at any specific wavelength of interest. These sources are therefore particularly well suited for applications in spectroscopy and metrology.

This work is carried out through collaborations with partner laboratories and is supported by the French National Research Agency.

Members : Patrick Georges, Sylvie Janicot, Gaëlle Lucas-Leclin
Former members : Paul Dumont, Iryna Gozhyk, Philippe Rigaud, 
Jonathan Staes

Dual-frequency optically-pumped VECSEL prototype
Schéma de principe d'un laser VECSEL bifréquence

• Dual-frequency VECSEL for coherent population trapping

We are interested in VECSEL architectures dedicated to CPT (Coherent Population Trapping) atomic clock experiments. The active structures are designed to emit on one of the transitions of the cesium atom (Cs) at 852 nm or 894 nm. The laser emission consists in two perpendicularly polarized laser lines, at two frequencies distant from 9.2 GHz corresponding to the hyperfine clock transition [1].

In this architecture, the frequency difference between the two laser lines is tunable, and the beat signal has a high spectral purity. We have demonstrated that it is possible to control the absolute frequency of the laser and the difference between the two frequencies. With this laser source, we have obtained a first CPT spectroscopy signal . We have particularly studied the different contributions to the laser noises (intensity, frequency, phase) and predicted that the intensity noise of the pump source would limit the short-term frequency stability of the atomic clock in the studied configuration [2,3].

• Structures actives et architectures laser

In collaboration with C2N, we evaluate the performances of active structures adapted to the VECSELs' requirements, for emission at the Cs lines D1 and D2. We are interested in the improvement of these structures.

In parallel, we investigate new pumping architectures (pump sources, dual spot configurations, etc.) to improve the performance of the dual-frequency laser source.

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